Consolidate the setup of the channel control register.  Prepare the
basic value in the preparation of the DMA descriptor, and write it into
the register upon descriptor execution.
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>